Liquid fuel for use in internal combustion engines and process for the production thereof



Patented July 28, 1931 UNITED STATES PATENT OFF-ICE WILFRED HERMANN HOFFEBT, OF LONDON, ENGLAND, ASSIGNOR TO NATIONAL IBENZOLE ASSOCIATION, OF LONDON, ENGLAND, A BRITISH COMPANY LIQUID FUEL FOR USE IN INTERNAL COMBUSTION ENGINES AND PROCESS FOR THE PRODUCTION THEREOF No Drawing. Original application filed October 19, 1927, Serial No. 227,360, and in Great Britain October 27, 1926. Divided and this application filed December 12, 1930. Serial No. 502,013.

This invention relates to liquid fuels for use in internal combustion engines and processes of production and treatment thereof.

The invention is applicable to the treatment in general of combustible organic liquids for use in such engines (including engines of the Diesel type), for example benzol, benzine, petrol, gasoline, cracked petrol, synthol, heavy oils and spirits produced by low temperature carbonization, berginization and the like, and other fuels from natural or artificial sources.

Such combustible organic liquids before the usual refining process frequently and in some cases invariably, contain a proportion of ingredients which give rise to resin formation. Immediately and for a short time after distillation such unrefined motor fuels, e. g. cracked petrol, may be comparatively free from non-volatile resinous matter but on storage or when used in internal combustion engines give rise to resinous material. The resinous material on storage may either remain dissolved in the liquid, or in certain cases may partially separate.

The chief troubles experienced when using these fuels are choking of jets by gummy material, and deposition of gummy or resinous material in the induction system e. g. on the inlet valves causing them to stick in their guides.

The object of this invention is to prevent or greatly reduce the resinification in such liquids, thus rendering it possible to store them for long periods without deterioration and to use them satisfactorily as fuels in internal combustion engines, thus avoidin 'lhe object of the invention is further to reduce or simplify the refining of the crude fuels particularly by eliminating unnecessary operations and avoiding large losses 'of valuable combustible ingredients while obtaining a fuel of satisfactory properties.

It is, in many cases, possible to prevent such resin formation by removing from the fuel those constituents which give rise to the resins e. g. unsaturated hydrocarbons but this is in many cases troublesome and expensive. In some cases e. g. cracked petrol g or considerably reducing refining losses.

these constituents are present in quite substantial proportions.

It has been recognized that if the fuels could be treated in some manner which would be capable of preventing resinification, there would be great advantages in using a fuel which has been refined as little as possible, in view of the economy of utilizing the whole of the unsaturated constituents and also because these constituents have valuable antiknock properties. But no such method of treatment is at present known, and accordingly there has been an important trend in research Work in the direction of selective removal of part of the unsaturated bodies, on the hypothesis that some of these bodies are less stable than others, so that if these less stable bodies could be removed the more stable bodies could be retained in the fuel with impunity.

Beginning my work from" this point of view, I made experiments on selective removal, after I had devised a method of test ing the stability of the fuel by exposing it to ultra violet radiation for a short time, in- '7 stead of leaving it to stand for several months. This test will be described hereafter and I will only say now that it has enabled me to accelerate the work enormously and thus to investigate the problem in detail. The results of selective removal of unsaturated bodies then showed that, although itis true that some unsaturated bodies are less stable than others, it is not true that a satisfactory separation can be achieved; the difference in stability appears to be merely a matter of degree. Accordingly I concluded that the problem cannot be solved satisfactorily by merely fractionally removing the unsaturated bodies.

I then compared the properties of a number of fuels of varying degrees of stability, as a result of which I was led to suspect that possibly the more stable fuels contained some body which acted as an inhibitor of resinification and ultimately I discovered that stability of unsaturated bodies depends on the presence of definite quantities of inhibitors, as well as, partly, on the absence of accelerators. Moreover I have been able to find a (ill number of suitable inhibitors, prominent among which are the aromatic phenolic and amino compounds. It is not sufficient merely to add haphazard quantities of these bodies to make an unstable fuel into a stable one,

for unrefined fuels may contain phenolic.

bodies and these may not be completely removed by the method of refining which has been adopted. Our experiments show that there is an optimum percentage of inhibitor, and if this percentage is largely exceeded, the body may act as an accelerator. Hence if a fuel naturally contains an inhibitor in substantial amount, addition of more inhibitor may reduce stablity instead of increasing it since the optimum percentage may be exceeded.

The optimum percentage varies with the fuel and with the particular inhibitor used; further, the optimum percentage varies with the time for which the fuel is to be stored, and the nature of the containing vessel. However, given these conditions, it is possible to determine the approximate optimum percentage by routine experiments based on the use of the ultra violet test I have described.

-The invention consists in the novel stabilized f-uels containing substantial proportions of unsaturated bodies, and also in the methods of stabilization, especially the addition of a predetermined percentage of inhibitor to a fuel initially free therefrom. One way of doing this is to refine the crude fuel to free it entirely from inhibitor in this case, for example, a simple alkali wash may be used to remove phenolic bodies and the .usual wash with concentrated sulphuric acid to remove unsaturated compounds or other treatment for the same purpose may be omitted, so that a very high yield of refined fuel is obtained, containing a high proportion of unsaturated bodies. Distillation will separate the fuel from the resins already formed, and then the addition of a definite (optimum) quantity of inhibitor will largely or entirely stabilize the fuel against further resinification on storage.

' The crude fuel ma also be treated in various other ways. ne alternative method consists in distillation in such a way as to obtain a refined fuel containing a known proportion of inhibitor (e. g. phenols) and this may be adjusted, if necessary by addition of further quantities of the inhibitor, to the optimum percentage for the type of storage contemplated.

The ideal inhibitor which may consist of a single substance or. a plurality of substances will have the following characteristic properties.

1. It must be capable of preventing or reducing the formation of resin.

2. The amount added must leave little or no residue on evaporation of the fuel.

3. It must not react with any of the constituents of the fuel to an extent which will give rise to any, or to any substantial, residue on evaporation or to objectionable by-products.

4. When added to the fuel it must have little or no effect upon an y metal or other engine parts with which it is likely to come in contact.

5. It must not prejudicially affect the normal combustion of the fuel to any serious extent.

6. It must be capable of dissolving or uniformly dispersing in the fuel.

It is desirable that a very small amount of the inhibitor should exhibit a large inhibiting effect.

Examples of inhibitors which may be employed are aromatic hydroxy, dihydroxy, and trihydroxy compounds e. g. phenols and cresols, amino compounds, amino phenols, and nitro aromatic compounds or combinations of these. My experiments uponvolatile hydrocarbon fuels such aspetrol and benzol have shown that the substances named are very effective in preventing resinification in these fuels. A

I have found that the tendency to resinification appears to be increased by certain substances, e. g. acids, aldehydes and mercaptans, decreased by others, e.- g. phenols, amino-phenols, nitrobenzene and amines, while some substances such as water, alcohols, ethers, thiophene and carbon bisulphide, appear to have little or no effect.

ome of the inhibitors may serve a double purpose e. g. aniline not only inhibits resinification but also removes traces of acidity developing in fuels containing alcohol.

The inhibitors need only be added in very small quantities and there appears to be an upper limit to the amount which has to be added. The amount to be added therefore must be between certain limits which are related both to the nature of the particular fuel and the conditions of storage (e. g. nature of the containing vessel, temperature, approximate time of storage and the like) or the conditions under which the fuel is to be used in an engine. In the examples which follow quantities of the order of 05% are employed and these may be regarded as a typical figure although the invention is not of course limited to this numerical proportion.

Some inhibition may be obtained by quantities of 1% or even more but the addition of such quantities is undesirable because of expense and still more because 1% or over may cause discolouration of the fuel on exposure to air and on standing. I prefer to add less than (one half of one per cent) and usua)lly less than 0.2% (one fifth of one per cent The ultra violet test may be performed by exposing samples of the fuel to ultra violet radiation for definite periods in dishes with quartz covers, placed in standard positions relative to the lamp, and the amount of radiation estimated by exposing potassium iodide solution in a standard position and titrating the amount of iodine liberated. The resinification appears to occur in two stages of which the second is more affected by ultra violet light so that in comparative experiments there should be the same period of time between distillation of the fuel and irradiation of the distillate.

Example 1 A cracked petrol gave on evaporation, before and after exposure to ultra violet radiation, residues respectively'of 188 and 445 milligrams per 100 cubic centimetres of petrol. After the addition of 0.035% by weight of tricresol it gave residues before and after exposure to ultra-violet radiations, of respectively 7 and 38 milligrams per 100 cublc centimetres of petrol. Tricresol is the name commonly given to 'a mixture consisting essentially of the 3 isomeric 0-, m-, and pcresols.

- Example 2 i the addition of 0.04% by weight of tricresol it gave residues before and after exposure to ultraviolet radiations of respectlvely 4 and 18 milligrams per 100 cubic centimetres.

Emample 3 A crude benzol gave on evaporation, before and after exposure to ultra violet radiations, residues respectively of 22 and 83 milligrams per 100 cubic centimetres of benzol. After the addition of 0.043% by weight of aniline it gave residues before and after exposure to ultraviolet radiations, of respectively 9.5 and 53 milligrams per 100 cubic centimetres of benzol.

These examples relate to fuel treatedin glass vessels. If the fuel is to be stored in tin or copper vessels, the test should be performed in such vessels since the nature of the containing vessel appears to influence the resinlfication very much in certain cases.

Example 1;

A crude benzol gave on evaporation from glass, tin, iron and copper vessels, resldues of 4.0, 4.0, 4.5, and 2.0 mgs. per 100 cc. re-

spectively. This benzol when stored for five.

'.,,-months in vessels of glass (light excluded),

tin, iron and copper, gave residues on evaporation from these materials of 480, 57, 42, and 37 mgs. per 100 cc. respectively. When 0.05%

. by weight of tricresol was added before storinhibitor depends on the time of storage contemplated. The relationship is somewhat complex but broadly speaking, a small percentage of inhibitor will stabilize a fuel against, say one months storage. After that time, the fuel may become less stable. If it is desired to make the fuel stable for say six months, it may be necessary to add more inhibitor (y), and the fuel thus treated, though not so good at the end of one month, will be better than the fuel containing as at the end of six months. Comparative experiments will elucidate this and similar points.

This application is a division of my copending application, Serial Number 227,360, filed October 19, 1927.

I declare that what I claim is:

1. The method of treating crude benzol containing resin forming constituents which comprises adding a minute proportion of an aromatic phenolic compound thereto.

2. The method of treating crude benzol containing resin forming constituents which comprises adding a minute proportion of an aromatic amino compound thereto.

3. The method of treating crude benzol containing resin forming constituents which comprises adding a minute proportion of an aromatic amino phenolic compound thereto.

4. Crude benzol containing resin forming constituents and a minute proportion of an added aromatic phenolic compound to prevent the formation of resins therein.

5. Crude benzol containing resin forming constituents and a minute proportion of an added aromatic amino compound to prevent the formation of resins therein.

6. Crude benzol containing resin-forming constituents and a minute proportion of an added aromatic amino phenolic compound to prevent the formation of resins therein.

7. The method of treating crude benzol containing resin-forming constituents which comprises adding a minute proportion of a cresol thereto.

8. The method of treating crude benzol containing resin-forming constituents which comprises adding a minute proportion of tricresol thereto.

9. The method of treating crude benzol containing resin-forming constituents which comprises adding a minute proportion of aniline thereto.

10. Crude benzol containing resin-forming constituents and a minute proportion of a cresol to prevent the formation of resins therein.

11. Crude benzol containing resin-forming constituents and a minute proportion of tricresol" to prevent the formation of resins therein.

12. Crude benzol containing resin-forming constituents and a minute proportion of aniline to prevent the formation of resins therein.

WILFRED HERMANN HOFFERT. 

